So I've tried removing some mods that might be causing issues similar to this, nothing seems to have fixed it. I don't really want to remove my mods and then see if it still happens as that doesn't really narrow down which mod is causing this, but I'm pretty sure it's a mod. It has to be.

Basically, my sims will "reset" when I have a controllable sim selected and I click on a guest sim (basically any sim that isn't controllable) to interact with them. Weirdly enough, it only resets the sim when I first click on the uncontrollable sim, and doesn't effect the interaction I select afterwards. This only happens when clicking on non-controllables. It'll also randomly happen when they choose to do something autonomously, but the interaction doesn't appear at all before the sim resets. Non-controllables interact with each other just fine.

What kind of mod could cause this if any?

Edit: I discovered I get the "Bad Gosub Tree Error" when enabling testingcheats. I believe this only happens when you have a mod that requires an EP you don't have installed, but I have all EPs and SPs installed.

"Bad Gosub Tree Error" will pop up when it can't find a file. That file can be a missing EP but can also be a custom made file. Do you have No Sim Loaded? That mod also requires Smarter EP Check by Cyjon (and a few other mods do to) check that you have that installed.

I did have it, then I removed it in hopes it'd fix the issue which it didn't.

I recently found an old post which shares my problem where you suggested using NSL with Smarter EP Check I believe, so I downloaded NSL again and this time made sure I had Smarter EP downloaded also, so I'm going to try it out now!

Edit: All seems good so far, thank you for your help!

Well it's not a suggestion so much as BoilingOil the creator of No Sim Loaded says on the description that his mod will not work without Smarter EP check. It pays to read over all of a mods descriptions before putting them into your game.

No Sim Loaded is not the only mod that needs Smarter EP Check but some other mods also require second files, not just that one.